Chronic wounds have an enormous impact on the US population. Between 1.3-3 million US individuals suffer from pressure ulcers (Kuehn (2007) JAMA 297:938-9; herein incorporated by reference). Of the 20 million Americans with diabetes, approximately 10-20% are at risk for developing diabetic ulcers (Kuehn (2007) JAMA 297:938-9; herein incorporated by reference). Many millions more suffer from venous stasis ulcers, lymphedema, peripheral vascular disease, non-healing surgical wounds, and burn wounds. It is estimated that between 5-10 billion dollars are spent annually in the US on wound care for chronic wounds (Kuehn (2007) JAMA 297:938-9; herein incorporated by reference).
By nature, all wounds contain some degree of bacteria. Wounds with increasing bacterial counts are said to be contaminated, then colonized, then critically colonized, and when the amount of bacteria exceeds 105 per gram of tissue, the wound is said to be “infected” although it may or may not display the classic characteristics of infection such as frank pus, inflammation, and erythema. Although grossly infected wounds may represent a situation that requires more urgent intervention, it has been demonstrated that any amount of bacteria in a wound is detrimental to wound healing. Acute infections may occur in “fresh” acute wounds or in chronic wounds and may lead to tissue loss, limb loss, sepsis, or even death.
The effect of bacteria on wound healing is multifactorial, the sum of which is referred to as the bioburden. In general, the bacteria compete with the host for oxygen and nutrients, and create a pro-inflammatory environment that resists host defenses and places a metabolic strain on the wound. Normal growth factors and other pro-healing mechanisms may be hindered or even degraded by the bacteria, the end result of which is that wound healing is greatly prolonged. Over time, through adhesion to each other and the secretion of a proteinaceous matrix, the bacteria may form a biofilm which may be resistant to further treatment (Galiano et al (2007) in Grabb and Smith's Plastic Surgery, Lippincott Williams & Wilkins, Philadelphia, Pa.; herein incorporated by reference).
Since the early 1900s, the mainstay of wound treatment has been irrigation and mechanical debridement. This technique decreases bacterial counts and removes foreign bodies and necrotic tissue in which bacteria can proliferate, and thus aids wound healing, decreases the incidence of infection, and reduces the bioburden of the wound.
As adjuncts to mechanical debridement and irrigation, there are currently several different types of chemical debridement and antimicrobial agents that are used to decrease bacterial counts and remove necrotic tissue. However, the efficacy of these agents in removing biofilm and debriding necrotic tissue is minimal, as they do not penetrate the wound eschar and thus cannot reach the places where bacteria may reside.
Negative pressure wound therapy (NPWT) is a recent advancement in wound care. Among other beneficial actions, NPWT devices help remove bacteria and their secreted enzymes, thereby reducing bacterial counts and subsequently aiding wound healing. However, NPWT devices should not be used if necrotic tissue or active infection is present, and will not remove a biofilm or eschar. In addition, these devices are not meant to be used in areas under pressure (such as in a sacral pressure sore) and also require a cavity or indentation in the skin, which limits their use in superficial wounds.
Pulse lavage irrigation has been developed over the last 40 years and has been repeatedly shown to effectively decrease bacterial counts in wounds more efficiently and effectively than conventional methods of irrigation, including bulb syringe irrigation or gentle lavage, and is as effective at reducing bacterial counts as tangential hydrodissection (Granick et al (2007) Ostomy Wound Manag. 53:64-6, 68-70, 72; herein incorporated by reference). Pulse irrigation can be used in wounds of any depth or level of bacteria. At moderate pressures, pulse irrigation is non-injurious to viable tissue. In a small scale study using a caprine wound model and bioluminescent strain of Pseudomonas aeruginosa, pulse irrigation was shown to reduce bacterial counts more effectively than bulb irrigation (Svoboda et al (2006) J Bone Joint Surg. Am. 88:2167-74; herein incorporated by reference). Finally, pulse lavage has been shown to be more effective than whirlpool therapy in reducing bacterial counts (Krasner et al (2007) Chronic wound care: A clinical source book for healthcare professionals, 4th ed, Alvern Pa., HMP Communications 331-342).
The major drawback to pulse lavage is that it is extremely messy and can easily contaminate the patient's surroundings, putting other patients and the person administering the treatment at risk. There have been case reports of pulse lavage irrigation spreading bacteria between patients (Maragakis et al (2004) JAMA 292:3006-11; herein incorporated by reference). Consequently, pulse lavage must be administered in a controlled environment. This limits the availability of pulse lavage as a therapeutic option and renders it unpracticable at the bedside, in home care and outpatient settings, and in military or field environments.
There is need in the art for improved methods of administering contained pulse lavage irrigation or contained pressurized non-pulsatile irrigation to aid wound healing.